Islam accepts, promotes, and preaches slavery  and has from its beginning. Mohammed kept slaves, and Islam promotes Mohammed and everything he did as the perfect example for all to follow. As a result, fewer centuries ago, Muslim slavers captured the Africans that were sold to Western slavers for transport and sale outside Africa. Even now, slavery continues in a number of Muslim countries and Middle Eastern authorities advocate jihad to capture victimes to be sold as slaves to help those countries reduce their debt levels.

Slavery provides other insights into Islam, through that same link to Mohammed and his actions. From my observation, there is nothing more racist and xenophobic than an Arab Muslim  and it would appear a Persian Muslim is not far behind. And it all comes from the Arabic language and the Islamic doctrine. It's not bad enough that Arabic commonly uses the same word for slave and for black African. These are people who are arrogant enough to believe their god speaks seventh century Arabic, incorporated in the Quran and since that time translated into modern Arabic so that modern Arabs and others can (perhaps) understand the words.

By contrast, what do we find in the West? The Catholic church prevented Muslim-style chattel slavery from existing in its areas of influence, ruling that one could own a man's work but not his soul. And then Western Protestants, English and American, ended slavery altogether in areas they controlled.

Westerners ended slavery where they could. Muslims continue it.

Colonizers? It seems to me that the West has now progressed to the point that it doesn't take over the places it feels it has to send its troops. Only the Muslims still do that, and insist of reconquering areas they once held. In fact, a look at history shows conquest is the only reliable way Islam has ever been spread.